chore: api examples to es6

[jajugoguma]

Please check if the PR fulfills these requirements

• It's submitted to right branch according to our branching model
• It's right issue type on title
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes/features)
• Docs have been added/updated (for bug fixes/features)
• It does not introduce a breaking change or has description for the breaking change

Description

• Change examples in api document(jsdoc) to ES6
• Prettier table of contents in README

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Thank you for your contribution to TOAST UI product. 🎉 😘 ✨

[lja1018]

리뷰완료합니다.

https://nhn.github.io/tui.rolling/latest/Rolling#event-afterMove
https://nhn.github.io/tui.rolling/latest/Rolling#event-beforeMove
여기도 화살표함수 적용하는게 어떨까요

[jungeun-cho]

[공통] 목차 윗내용 제거랑 네임스페이스 사용하는방법 Browser 표기 확인해주세요